From the Research
Chlorpyriphos and Intermediate Syndrome
- Chlorpyriphos is an organophosphate insecticide that can cause intermediate syndrome (IMS) in humans 1, 2, 3.
- IMS is a condition that occurs after apparent recovery from the acute cholinergic syndrome, characterized by weakness of the muscles of respiration and proximal limb muscles 4.
- The exact mechanism of IMS is not fully understood, but it is thought to be related to the inhibition of acetylcholinesterase and the subsequent accumulation of acetylcholine at the neuromuscular junction 4, 2.
Evidence of Chlorpyriphos-Induced Intermediate Syndrome
- A case report described a patient who ingested chlorpyriphos and developed IMS, characterized by muscular weakness, hypotonia, arreflexia, and recumbent dyspnea requiring ventilatory support 1.
- A prospective cohort study found that prolonged jitter in single fibre electromyography (SfEMG) within the first 24 hours of exposure to chlorpyriphos was associated with an increased risk of IMS 2.
- Another case report described a patient who self-administered chlorpyriphos subcutaneously and developed severe and prolonged neurologic toxicity, including IMS and distal peripheral neuropathy 3.
Electrophysiological Correlates of Intermediate Syndrome
- Electrophysiological studies have shown that IMS is associated with characteristic phenomena, including repetitive firing, decrement-increment response, and decrementing response 4, 5, 2.
- SfEMG has been used to predict the development of IMS in patients exposed to organophosphate insecticides, including chlorpyriphos 2.
- The time course of electrophysiological recovery of the neuromuscular junction has been shown to be similar to the time course of respiratory recovery in IMS patients 2.